JP2003061070A - Catv transmission system and transmitter/receiver for the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CATV transmission system that eliminates the need for frequency conversion for incoming and outgoing communication bands, avoids incoming band from being limited and allows one coaxial cable, to conduct reception of a CATV outgoing signal and two-way communication. SOLUTION: The CATV transmission system configures incoming and outgoing signals, such that an outgoing (in the direction of subscriber terminals from a CATV center facility) CATV signal F3/F4 with a high-frequency band and incoming (in a direction of the CATV center facility from the subscriber terminals) and outgoing communication signals F1/F2 with a low-frequency band are frequency-multiplexed, and the incoming and outgoing communication signals F1/F2 are time-division multiplexed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CATV (cabl).
E-Television) transmission system and an optical transceiver used in the system
CA in which the V signal and the upstream and downstream communication signals are superimposed and transmitted.
The present invention relates to a TV transmission system and an optical transmitter / receiver used in the system.

[0002]

2. Description of the Related Art FIG. 16 is a diagram showing an example of frequency allocation in a conventional CATV transmission system. Referring to the figure, the conventional CATV transmission system divides the frequency band into two, and descends the high frequency side wide band (from the CATV center device to the subscriber terminal) CATV signal band F11, downstream communication band F12, and maintenance / operation signals. Generally, a method of frequency-dividing and assigning to the band F13 and the like, and assigning the low-frequency narrow band to the communication band F14 (up from the subscriber terminal to the CATV center apparatus) and various supervisory signal bands F15 by frequency-dividing Has been done. A stop band (separation band) F16 is provided between the upstream communication band F14 and the downstream CATV signal band F11.

An example of this type of technology is disclosed in Japanese Patent Laid-Open No. 2000-
No. 13774, Japanese Patent Laid-Open No. 2000-50228,
JP-A-2000-68944, JP-A-9-9316
No. 7, JP-A-9-153873, JP-A 9-2
It is disclosed in Japanese Patent Laid-Open No. 19686 and Japanese Patent Laid-Open No. 10-108161.

A CATV transmission system is also known in which a CATV downlink signal is received and bidirectional communication using the same frequency band is performed using a plurality of coaxial cables.

[0005]

However, the conventional CAT
In order to perform communication on the V transmission, the basic transmission / reception frequency (base band) of the communication terminal is frequency-converted into an upstream low frequency communication band and a downstream high frequency communication band on the CATV transmission path to perform bidirectional transmission, and the receiving terminal device. Therefore, it was necessary to convert the frequency to the basic transmission / reception frequency again.

At the present time when the demand for communication is increasing,
Since the downstream CATV signal requires a wide band, the upstream band is limited, and there is a problem that the communication band is insufficient.

Further, there is a drawback that a plurality of coaxial cables are required to simultaneously perform reception of a CATV downlink signal and bidirectional communication using the same frequency band.

Therefore, an object of the present invention is that there is no need to frequency-convert the upstream and downstream communication bands, the upstream band is not limited, and the CATV downstream signal reception and bidirectional communication using the same frequency band. It is to provide a CATV transmission system capable of performing the above-mentioned operations with a single (one) coaxial cable, and an optical transmission / reception device used in the system.

[0009]

In order to solve the above-mentioned problems, a CATV transmission system according to the present invention has a first frequency band downlink (direction from CATV center equipment to subscriber terminal) C
ATV signal and upstream of a second frequency band narrower in frequency and narrower than the first frequency band (from the subscriber terminal to the CAT
The V center equipment direction) and the downlink communication signal are frequency-superposed, and the uplink and downlink communication signals are time-division multiplexed.

Further, the upstream and downstream signal transmitting apparatus according to the present invention comprises a downstream (from the CATV center equipment to the subscriber terminal) CATV signal of the first frequency band and a second narrow band which is lower in frequency than the first frequency band. It is characterized in that it is used in a CATV transmission system in which frequency upstream (downward from subscriber terminals to CATV center equipment) and downstream communication signals are frequency-superimposed, and the upstream and downstream communication signals are time-division multiplexed.

The upstream and downstream signal receiving apparatus according to the present invention comprises a downstream (from the CATV center facility to the subscriber terminal) CATV signal in the first frequency band and a second narrow band which is lower in frequency than the first frequency band. It is characterized in that it is used in a CATV transmission system in which frequency upstream (downward from subscriber terminals to CATV center equipment) and downstream communication signals are frequency-superimposed, and the upstream and downstream communication signals are time-division multiplexed.

Further, the center device according to the present invention is the downlink of the first frequency band (from the CATV center equipment to the subscriber terminal).
A CATV signal and a second frequency band that is narrower than the first frequency band and narrower in frequency (from the subscriber terminal to the CA
A center device for use in a CATV transmission system in which a TV center equipment direction) and a downlink communication signal are frequency-superposed, and the uplink and downlink communication signals are time-division multiplexed, the downlink CATV signal and the downlink communication signal. A frequency superimposing means for superimposing the frequency and a combining means for combining the upstream and downstream communication signals.

Also, the node device according to the present invention is a downlink (in the direction from a CATV center facility to a subscriber terminal) CATV signal of a first frequency band and an upstream of a second frequency band narrower in frequency and narrower than the first frequency band. A node device for use in a CATV transmission system in which a subscriber terminal and a downstream communication signal are frequency-superimposed, and the upstream and downstream communication signals are time-division multiplexed. It is characterized by including an optical / electrical conversion means for converting the frequency-superimposed signal with the downlink communication signal into an electrical signal, and an electrical / optical conversion means for converting the upstream communication signal into an electrical signal.

According to the present invention, it is not necessary to frequency-convert the upstream and downstream communication bands by the above configuration, the upstream band is not limited, and both reception of a CATV downstream signal and use of the same frequency band are performed. It is possible to perform directional communication with a single (single) coaxial cable.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of the best mode of the CATV transmission system according to the present invention. Referring to FIG. 1, a CATV transmission system includes a center side optical transceiver (hereinafter referred to as an optical center device) 1,
Node side optical transceiver (hereinafter referred to as optical node device) 1
1 and 1.

The optical center device 1 receives the downstream CATV signal transmitted from the CATV center equipment 111,
A function of transmitting this to the optical node device 11 and a downlink communication signal transmitted from the CATV center equipment 111,
The function of transmitting this to the optical node device 11 and the reception of the upstream communication signal transmitted from the optical node device 11
It also includes a function of transmitting to the ATV center equipment 111.

Further, the optical node device 11 has a function of receiving the downlink CATV signal transmitted from the optical center device 1 and transmitting it to the subscriber terminal 121, and a downlink communication signal transmitted from the optical center device 1. The subscriber terminal 121
And a function of receiving the upstream communication signal transmitted from the subscriber terminal 121 and transmitting this to the optical center apparatus 1.

Here, the frequency arrangement of the CATV transmission system according to the present invention will be described before describing each component. 2 is a frequency allocation diagram of the CATV transmission system according to the present invention, FIG. 3 is a timing chart of each signal,
FIG. 4 is a diagram in which signals of the CATV transmission system according to the present invention are displayed using a frequency axis and a time axis.

Referring to FIG. 2, upstream and downstream (hereinafter, referred to as
Communication signals are referred to as "uplink / downlink".
The same low frequency band up to (F1 <F2) is allocated,
Frequency F3 higher than frequency F2 for downlink CATV signals
To F4 (F2 <F3 <F4) are assigned. The frequencies F2 to F3 are in the stop band (separation band) as in the conventional example.

Next, referring to FIG. 3, the downstream CATV signals F3 / F4 are continuously transmitted, while the downstream communication signals F1 / F2 and the upstream communication signals F1 / F2 are time-divisionally, that is, It indicates that they are transmitted alternately.

Next, referring to FIG. 4, this figure is a diagram in which the frequency arrangement of FIG. 2 and the operation of FIG. 3 are displayed together. The downlink CATV signal F3 / F4 and the uplink / downlink communication signal F1 / F are shown.
It is displayed that a different frequency band is assigned to 2, the same frequency band is assigned to the upstream / downstream communication signals F1 / F2, and that the upstream / downstream communication signals F1 / F2 are time division multiplexed signals. ing.

Next, returning to FIG. 1, each component will be described. In the figure, an optical center device 1 is a downlink optical transmitter (FT) that transmits a downlink CATV signal in a high frequency band and a downlink communication digital signal in a low frequency band, which are frequency band-divided.
X) 2, an upstream optical receiver (RRX) 3 that receives an upstream communication digital signal in a low frequency band, and a coupler (HYB) that couples the downstream communication digital signal and the upstream communication digital signal of single-line time division bidirectional transmission. ) 4 and down CAT of high frequency band
It includes a directional filter (DF) 5 for combining the V signal and the downstream communication digital signal in the low frequency band.

Further, the optical node device 11 is a downstream optical receiver (FR) for receiving a downstream CATV signal in a high frequency band and a downstream communication digital signal in a low frequency band, which are frequency band-divided.
X) 12, an upstream optical transmitter (RTX) 13 that transmits a low frequency band upstream communication digital signal, and a directional filter (DF) that separates a high frequency band downstream CATV signal and a low frequency band downstream communication digital signal. ) 15, a combiner (HYB) 14 for combining the downlink communication digital signal and the uplink communication digital signal of the one-time-division bidirectional transmission, and the downlink C of the high frequency band separated and output by the directional filter (DF) 15.
It includes a directional filter (DF) 16 for recombining the ATV signal and the low frequency band single-line time division two-way communication digital signal combined by the combiner 14.

The above optical center device 1 and optical node device 1
By combining 1, the two transmission paths of the downstream CATV signal in the high frequency band of the optical center device 11 and the single-section time-division communication signal in the low frequency band are separated and combined, and the output of the optical node device 11 (subscriber terminal 121 On the side), the downstream CATV signal and the time-division bidirectional communication signal can be superimposed and transmitted on a single coaxial cable.

Next, the operation of this embodiment will be described. In the figure, an optical center device 1 has a downstream CAT of a high frequency band divided into frequency bands on the input / output side of an electric signal.
A V signal input terminal a, an input / output shared terminal b for a low frequency band single-line time-division bidirectional communication signal, and an optical signal input / output side,
It has a downstream light output terminal c and an upstream light input terminal d.

The optical node device 11 has a downstream optical input terminal e, an upstream optical output terminal f on the optical signal input / output side, and an input / output common terminal g on the electrical signal input / output side. I have it.

Then, the downstream CATV signal in the high frequency band is input to the input terminal a, and the one-time-division bidirectional communication signal in the low frequency band is input / output by converting the downstream communication signal and the upstream communication signal into a time-division burst format. Input and output to the common terminal b.

The downstream communication signal in the low frequency band is input to the low-pass filter input terminal (L) of the directional filter (DF) 5 via the coupler 4, and the downstream CATV signal in the high frequency band is directional filter. Input to the high-pass filter input terminal (H) of (DF) 5.

Then, the directional filter (DF) 5 is used for downward CA.
A downlink signal (electrical signal) obtained by frequency-superimposing a TV signal and a downlink communication signal is electrically / optically converted by the downlink optical transmitter (FTX) 2 into an optical signal, which is sent from the optical output terminal c to the optical fiber transmission line.

The downstream optical signal is transmitted to the optical receiver (FRX) 12 of the optical node device 11 via the downstream optical input terminal e.
Directionally filtered (DF) 1
5 is input to the common terminal.

The high-pass filter output (H) of the directional filter (DF) 15 outputs a downstream CATV signal, and the low-pass filter output (L) outputs a downstream communication signal.

The downward CATV signal is directly fed to the directional filter (D
F) 16 is input to the high-pass filter (H), and the downlink communication signal is passed through the coupler (HYB) 14 to the directional filter (DF) 1
6 is input to the low-pass filter (L), and each downlink signal is frequency-superimposed again and sent from the input / output common terminal g of the optical node device 11 to the subscriber terminal 121 side.

On the other hand, the upstream communication signal (electrical signal) transmitted from the subscriber terminal 121 is input to the input / output common terminal g of the optical node device 11, and the low pass filter (L) of the directional filter (DF) 16 is input. ) To the common terminal of the coupler (HYB) 14 and further connected to the input of the upstream optical transmitter 13.

The upstream communication signal which has been converted into an optical signal by the upstream optical transmitter 13 into an optical signal is sent from the upstream optical output terminal f to the optical fiber transmission line.

The upstream optical signal is converted into an electrical signal by being optically / electrically converted by the optical receiver 3 of the optical center device 1 via the upstream optical input terminal d, and the input / output is shared from the common terminal of the coupler (HYB) 4. It is output to the CATV center equipment 111 via the terminal b.

In the present invention, as shown in FIG. 4, the frequency structure of the downstream CATV signal is different from that of the upstream / downstream communication signal, that is, the downstream CATV signal has a high frequency band from frequencies F3 to F4. / Low frequency bands from frequencies F1 to F2, which are lower in frequency than frequency F3, are assigned to the downlink communication signals, respectively, and the same frequency band is assigned to the uplink and downlink communication signals. Since it is configured to be transmitted in time division, there is no need to frequency-convert the upstream and downstream communication bands, and the reception of the CATV downstream signal and the bidirectional communication using the same frequency band are provided in one line (one line). It can be done with a cable. As will be described later, the upstream band can be expanded by having a configuration in which the band of the CATV downstream signal and the upstream / downstream communication band are variable in correspondence with the digitization of television broadcasting.

[0037]

EXAMPLES Examples of the present invention will be described below. First, the first embodiment will be described. The first embodiment relates to a directional filter. 5 is a circuit diagram of the directional filter shown in the first embodiment, FIG. 6 is a plan view of the directional filter, FIG. 7 is a front view of the directional filter, and FIG. 8 is a left side view of the directional filter. is there.

Corresponding to this directional filter are the directional filters (DF) 5, 15 and 16 shown in FIG. Referring to FIG. 5, directional filters (DF) 5, 15 and 16 are a low-pass filter formed by combining coils L1 to L4 and capacitors C1 to C3, and a capacitor C.
4 to C10 and coils L5 to L7 in combination, and a high-pass filter (high-pass filter). In the figure, as an example, the input signal (frequency band 10 to 750M
Output signal 1 (low frequency narrow band signal of frequency band 10 to 50 MHz) and output signal 2 (frequency band 70 to 7).
A directional filter (DF) for dividing and outputting a high-frequency broadband signal of 50 MHz) is displayed.

Next, FIGS. 6 to 8 show an example of a detachable (plug-in type) directional filter. That is, the inductance of the coils L1 to L7 and the capacitors C1 to C
A plurality of directional filters having different capacitances 10 are prepared, which are made detachable and can be replaced if necessary. As can be seen with reference to FIGS. 7 and 8, the directional filter includes a body 31 and pins 32-1 to 32-n.
(N is a positive integer) and On the other hand, an external view of an example of a socket to which this directional filter is attached is shown in FIG. The socket 33 is attached to a predetermined place of the optical center device 1 and the optical node device 11. That is, if a plurality of detachable directional filters having different separation frequencies (cut-off frequencies) are prepared, by exchanging the directional filters whose separation frequency is shifted to a higher frequency side than the current one, for example, the upstream band (Communication band) can be expanded. That is, even if the occupied band of the downlink CATV signal is narrowed by digitizing the television broadcasting, it is possible to distribute a larger amount of information as compared with the conventional one, so that the upstream band can be expanded. .

Next, the second embodiment will be described. Second
In the embodiment, the monitoring device (S
MT: Supervision Monitoring
Transponder). Figure 1
Reference numeral 0 is a configuration diagram of the second embodiment. In the figure,
The same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

Referring to the figure, the monitoring device (SMT) 2
2 is a downstream optical receiver (FRX) 12 and an upstream optical transmitter (R
TX) 13, combiner (HYB) 14 and directional filter (D
F) is connected to the interface 21 inserted between The monitoring device (SMT) 22 receives the received light power of the downstream optical receiver (FRX) 12 and the upstream optical transmitter (RT
X) 13 light emission power is monitored.

The operation will be described in detail. The monitoring device (S
MT) 22 measures the received light power of the downstream optical receiver (FRX) 12 and the emitted light power of the upstream optical transmitter (RTX) 13, and the measurement result is transmitted via the interface 21 and the optical center device 1 to the CATV center equipment 111. Send to. on the other hand,
The CATV center equipment 111 that receives the measurement result receives the interface 2 between the optical center device 1 and the optical node device 11.
A control signal corresponding to the measurement result is sent back to the monitoring device (SMT) 22 via 1. The monitoring device (SMT) 22 operates according to the control signal.

Next, a third embodiment will be described. Third
The embodiment relates to a monitoring device provided in the optical center device 1. FIG. 11 is a block diagram of the third embodiment. Note that, in the figure, the same components as those in FIG.

Referring to the figure, the monitoring device (SMT) 2
3 is a downstream optical transmitter (FTX) 2 and an upstream optical receiver (RR)
X) 3 and the interface 24 inserted between the terminal b and the coupler (HYB) 4. Then, the monitoring device (SMT) 23 monitors the light emission power of the downstream optical transmitter (FTX) 2 and the received light power of the upstream optical receiver (RRX) 3.

The operation will be specifically described. The monitoring device 23
Measures the light emission power of the downstream optical transmitter (FTX) 2 and the received light power of the upstream optical receiver (RRX) 3, and the measurement result is transmitted via the interface 24 to the CATV center equipment 11
Send to 1. On the other hand, the CATV center equipment 111 that has received the measurement result sends back a control signal corresponding to the measurement result to the monitoring device (SMT) 23 through the interface 24 of the optical center device 1. The monitoring device (SMT) 23 operates according to the control signal.

Next, a fourth embodiment will be described. Fourth
The embodiment relates to an amplifier provided in the optical node device 11. FIG. 12 is a block diagram of the fourth embodiment. Note that, in the figure, the same components as those in FIG. Referring to FIG. 1, an amplifier (eg, operational amplifier) 25 is inserted between the coupler (HYB) 14 and the directional filter (DF) 15,
An amplifier (for example, operational amplifier) 26 is inserted between the coupler (HYB) 14 and the upstream optical transmitter (RTX) 13. These amplifiers 25 and 26 amplify the pulse only when the pulse is input. That is, when the pulse of the downstream communication signal is output from the low pass filter (L) of the directional filter (DF) 15, the amplifier 25 amplifies the pulse and the pulse of the upstream communication signal is output from the combiner (HYB) 14. Is output, the amplifier 26 amplifies the pulse.

These amplifiers 25 and 26 are connected to the optical node device 1
1 is not only capable of amplifying the upstream / downstream communication digital signal, but also the amplifiers 25, 26.
Since only a pulse is amplified, noise having a threshold value or less can be eliminated. In addition,
Although the monitoring device (SMT) 22 is also included in the configuration in the figure, it is also possible to omit this.

An amplifier 27 is inserted between the high-pass filters (H) of the directional filters (DF) 15 and 16, and the amplifier 27 is provided outside via the amplifier (AMP) output terminal. It is also possible. Similarly, amplifiers 25, 2
The amplification device composed of 6 and the coupler (HYB) 14 can also be provided outside via an amplifier (AMP) output terminal provided separately from the amplifier (AMP) output terminal.

Next, a fifth embodiment will be described. Fifth
The embodiment relates to another example of the amplifier provided in the optical node device 11. FIG. 13 is a block diagram of the fifth embodiment. Note that, in the figure, the same components as those in FIG. Referring to the figure, the interface 21 and the directional filter (DF)
An amplifying device 35 is inserted between the 16 low-pass filters (L). The amplification device 35 includes a combiner (HYB) 3
6, 37 and amplifiers (for example, operational amplifiers) 38, 39
And a combiner (HYB) 36 and a combiner (HYB)
An amplifier 38 is inserted between one terminal of 37, and an amplifier 39 is inserted between the other terminal. These amplifiers 3
Reference numerals 8 and 39 are for amplifying the pulse only when the pulse is input. That is, when a pulse of the downlink communication signal is output from the low pass filter (L) of the directional filter 15, the combiner (HYB) 14, the interface 21, and the combiner (HY).
The amplifier 38 amplifies the pulse via B) 36, and when a pulse of the upstream communication signal is output from the low pass filter (L) of the directional filter (DF) 16, it passes through the combiner (HYB) 37. The amplifier 39 amplifies the pulse.

The effect of providing the amplifying device 35 in the optical node device 11 is the same as that of the above-mentioned fourth embodiment, and therefore its explanation is omitted. Although the monitoring device 22 is also included in the configuration in the figure, it is also possible to omit this.

An amplifier 27 is inserted between the high-pass filters (H) of the directional filters (DF) 15 and 16, and the amplifier 27 is provided outside via the amplifier (AMP) output terminal. It is also possible. Similarly, the amplification device 35
Also, it is possible to provide it externally via an amplifier (AMP) output terminal provided separately from the amplifier (AMP) output terminal.

Further, as shown in FIG.
Of the directional filters (DF) 15 and 16, the amplifier 27, and the coupler (HYB) 1 between the output terminal g of the
4, it is also possible to insert a repeater (REP) 41 including the interface 21 and the amplification device 35. Downlink C by the amplifier 27 of the repeater 41
The ATV signal is amplified, and the amplification device 35 of the repeater 41 amplifies the upstream and downstream communication signals. When the repeater 41 is inserted in such a coaxial portion, a coupler (HY
B) 14 is unnecessary. The coupler (HYB) 36 and the directional filter (DF) 15 may be directly connected. In addition, the coupler (H
When the YB) 14 is used, the coupler (HYB) 14 and the optical transmitter (RTX) 13 are separated from each other, and the optical transmitter (RTX) 1
A resistor is connected instead of 3, and the other end of the resistor is grounded (terminated).

This is because when the subscriber terminal 121 is, for example, a terminal of an apartment house, a large number of terminals are connected to the output terminal g of the optical node device 11, so that the optical node device 11 is connected to the terminal of the apartment house. There may be a lack of transmit power level to. Therefore, this problem can be solved by inserting the repeater (REP) 41 between the optical node device 11 and the terminal of the housing complex to raise the level of transmission power.

When the upstream communication signals from a plurality of terminals in an apartment house are input to the optical node device 11, so-called ingress noise may occur. This repeater (REP)
There is also an effect that the ingress noise is reduced by inserting.

A router for connecting networks to each other by the bidirectional amplifier circuit composed of the amplifiers 25 and 26 and the coupler 14 shown in FIG. 12 and the bidirectional amplifier circuit (amplifier 35) shown in FIG. It is also possible to realize with (router).

Next, a sixth embodiment will be described. Sixth
The embodiment relates to a changeover switch provided in the optical center device 1 and the optical node device 11. 14 and 15 are configuration diagrams of the sixth embodiment. In the figure, the same components as those in FIG.
The description is omitted. FIG. 14 shows an example of a changeover switch provided in the optical center device 1, and FIG. 15 shows an example of a changeover switch provided in the optical node device 11.

First, the changeover switch in the optical center device 1 will be described with reference to FIGS. 14 and 1. Referring to FIG. 1, a coupler (HYB) 4 was used for switching between an upstream communication signal and a downstream communication signal in the optical center device 1, but in the sixth embodiment, this coupler (HYB) 4 is used instead. Switch 42 (see FIG. 14) is used. That is, the changeover switch 42 is mechanically changed over by a control signal from the outside.

Next, the changeover switch in the optical node device 11 will be described with reference to FIGS. 15 and 1. Figure 1
Referring to, the optical node device 11 uses the coupler 14 for switching between the upstream communication signal and the downstream communication signal.
In the sixth embodiment, the changeover switch 4 is used instead of the coupler 14.
3 (see FIG. 15) is used. That is, the changeover switch 43 is mechanically changed over by a control signal from the outside.

That is, when a control signal for transmitting a downlink communication signal is input to the changeover switches 42 and 43 from the outside, the changeover switch 42 is connected to the low pass filter (L) side of the directional filter (DF) 5. And the downlink communication signal is transmitted to the directional filter (D
F) 5 is output to the low pass filter (L). Further, the changeover switch 43 is a low-pass filter (L) of the directional filter (DF) 15.
The downstream communication signal from the low pass filter (L) of the directional filter (DF) 15 is output to the low pass filter (L) of the directional filter (DF) 16.

On the other hand, when a control signal for transmitting the upstream communication signal is input to the changeover switches 42 and 43 from the outside, the changeover switch 43 is connected to the upstream optical transmitter (RTX) 13 side to transmit the upstream communication signal. It is output to the optical transmitter (RTX) 13. Further, the changeover switch 42 is an optical receiver (RR
X) is connected to the 3 side, and the upstream communication signal is transmitted through the terminal b to C
It is output to the ATV center equipment 111.

The control signal switching timings are, for example, the timings shown in the downlink F1 / F2 and the uplink F1 / F2 in FIG. That is, down F1 / F2 and up F1
/ F2 is switched alternately.

[0062]

According to the CATV transmission system of the present invention, the downstream CATV signal of the first frequency band (from the CATV center equipment to the subscriber terminal) and the second frequency of the narrow band which is lower than the first frequency band. Since the upstream (downstream from the subscriber terminal to the CATV center equipment) and downstream communication signals are frequency-superposed and the upstream and downstream communication signals are time-division multiplexed, there is no need to frequency-convert the upstream and downstream communication bands. It is possible to perform reception of a CATV downlink signal and bidirectional communication using the same frequency band using a single (one) coaxial cable without any restriction on the upstream band. Further, other inventions according to the present invention have the same effects as the above-mentioned present invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a best mode embodiment of a CATV transmission system according to the present invention.

FIG. 2 is a frequency allocation diagram of a CATV transmission system according to the present invention.

FIG. 3 is a timing chart of each signal.

FIG. 4 is a diagram in which a signal of the CATV transmission system according to the present invention is displayed using a frequency axis and a time axis.

FIG. 5 is a circuit diagram of the directional filter shown in the first embodiment.

FIG. 6 is a plan view of the same-direction filter.

FIG. 7 is a front view of the same-direction filter.

FIG. 8 is a left side view of the same-direction filter.

FIG. 9 is an external view of an example of a socket to which a directional filter is attached.

FIG. 10 is a configuration diagram of a second embodiment.

FIG. 11 is a configuration diagram of a third embodiment.

FIG. 12 is a configuration diagram of a fourth embodiment.

FIG. 13 is a configuration diagram of a fifth embodiment.

FIG. 14 is a configuration diagram of a sixth embodiment.

FIG. 15 is a configuration diagram of a sixth embodiment.

FIG. 16 is a diagram showing an example of frequency allocation in a conventional CATV transmission system.

[Explanation of symbols]

1 Center side optical transceiver 2 Downstream optical transmitter 3 upstream optical receiver 4, 14 combiner 5, 15, 16 directional filter 11 Optical node equipment 12 Downstream optical receiver 13 Upstream optical transmitter 22, 23 Monitoring device 25, 26, 27 amplifier 31 Directional filter body 32 pins 35 Bidirectional amplifier 38, 39 amplifier 41 Repeater 42, 43 selector switch

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) H04L 5/14 H04N 7/08 Z 5K028 H04N 7/08 H04B 9/00 C 7/081 G 7/22 F term (reference) ) 5C063 AB06 AB07 CA23 DA01 DA20 5C064 BA01 BB05 BC10 BC11 BC12 BC13 BC14 BC16 BC20 BD01 BD07 5K002 AA05 CA03 DA02 DA03 FA01 GA01 5K018 AA03 BA02 BA03 CA06 5K022 AA01 AA11 AA21 FF02 5K028 AA11 AA17 02

Claims (31)

[Claims] 1. A downlink of a first frequency band (in the direction from a CATV center facility to a subscriber terminal) and a CATV signal and an uplink of a second frequency band having a narrower band than the first frequency band (from the subscriber terminal to the CATV center). (Equipment direction) and the downlink communication signal are frequency-superposed, and the uplink and downlink communication signals are time-division multiplexed.
Transmission system. 2. A center device and a node device are provided between the CATV center facility and the subscriber terminal, and the CATV signal and the downlink communication signal from the CATV center facility are frequency-controlled by the center device. Characterized in that it is superimposed and inputted to the subscriber terminal through the node device, and the upstream communication signal from the subscriber terminal is inputted into the CATV center facility through the node device and the center device. The CATV transmission system according to claim 1. 3. The CATV signal and the downlink communication signal are electrically / optically converted by the center device, and then further optically / electrically converted by the node device, and the upstream communication signal is electrically converted by the node device. 3. The CATV transmission system according to claim 2, wherein after the optical conversion, the center device further performs optical / electrical conversion. 4. An optical fiber for transmitting the CATV signal and the downlink communication signal and an optical fiber for transmitting the uplink communication signal are separately provided between the center device and the node device, and the node device and The CATV transmission system according to claim 2 or 3, wherein a single coaxial cable is provided between the subscriber terminals. 5. A downlink of a first frequency band (from a CATV center facility to a subscriber terminal) and a CATV signal and an uplink of a second frequency band narrower in frequency and narrower than the first frequency band (from the subscriber terminal to the CATV center). Equipment direction) and a downlink communication signal are frequency-superposed, and the uplink and downlink signal transmission device in a CATV transmission system in which the uplink and downlink communication signals are time-division multiplexed. 6. A center device and a node device are provided between the CATV center facility and the subscriber terminal, and the CATV signal and the downlink communication signal from the CATV center facility are frequency-shifted by the center device. Characterized in that it is superimposed and inputted to the subscriber terminal through the node device, and the upstream communication signal from the subscriber terminal is inputted into the CATV center facility through the node device and the center device. The upstream and downstream signal transmitter according to claim 5. 7. The CATV signal and the downlink communication signal are electrically / optically converted by the center device, and then further optically / electrically converted by the node device, and the upstream communication signal is electrically converted by the node device. 7. The upstream / downstream signal transmission device according to claim 6, wherein after the optical conversion, the center device further performs optical / electrical conversion. 8. An optical fiber for transmitting the CATV signal and the downlink communication signal and an optical fiber for transmitting the uplink communication signal are separately provided between the center device and the node device, and the node device and 8. The upstream / downstream signal transmission apparatus according to claim 6, wherein a single coaxial cable is provided between the subscriber terminals. 9. A down stream of a first frequency band (from a CATV center facility to a subscriber terminal) a CATV signal and an up stream of a second frequency band having a narrower band than the first frequency band (from the subscriber terminal to the CATV center). Equipment direction) and a downlink communication signal are frequency-superposed, and the uplink and downlink signal receiving apparatus in a CATV transmission system in which the uplink and downlink communication signals are time-division multiplexed. 10. A center device and a node device are provided between the CATV center facility and the subscriber terminal, and the CATV signal and the downlink communication signal from the CATV center facility are frequency-shifted by the center device. Characterized in that it is superimposed and inputted to the subscriber terminal through the node device, and the upstream communication signal from the subscriber terminal is inputted into the CATV center facility through the node device and the center device. The upstream and downstream signal receiving device according to claim 9. 11. The CATV signal and the downlink communication signal are electrically / optically converted by the center device, and then further optically / electrically converted by the node device, and the uplink communication signal is electrically converted by the node device. 11. The upstream / downstream signal receiving apparatus according to claim 10, wherein after the optical conversion, the center apparatus further performs optical / electrical conversion. 12. An optical fiber for transmitting the CATV signal and the downlink communication signal and an optical fiber for transmitting the uplink communication signal are separately provided between the center device and the node device, and the node device and The uplink / downlink signal receiving apparatus according to claim 10 or 11, wherein a single coaxial cable is provided between the subscriber terminals. 13. Downstream of a first frequency band (from CATV center equipment to a subscriber terminal) CATV signal and upstream of a second frequency band of a low frequency narrower than the first frequency band (subscriber terminal) From the CATV center equipment direction) and the downlink communication signal, and the downlink CATV signal and the downlink communication signal are used in a CATV transmission system in which the uplink and downlink communication signals are time-division multiplexed. A center device, comprising: a frequency superimposing means for superimposing a frequency of the above and a combining means for combining the upstream and downstream communication signals. 14. An electric / optical conversion means for converting the signal on which the frequency is superposed by the frequency superposition means to electric / optical conversion, and an optical / electric conversion means for converting the upstream communication signal to electric / electricity. 14. The center device according to claim 13, wherein the center device is a center device. 15. The center device according to claim 13, wherein the frequency superimposing means is a directional filter. 16. The center device according to claim 15, wherein the directional filter is configured to be replaceable so that a separation frequency band can be arbitrarily set. 17. The center apparatus according to claim 13, further comprising monitoring means for monitoring the downlink CATV signal and the uplink and downlink communication signals. 18. The center device according to claim 13, wherein the coupling means is composed of a changeover switch which is controlled by a time division control signal. 19. Downstream of a first frequency band (from CATV center equipment to subscriber terminal) CATV signal and upstream of a second frequency band of a low frequency narrower than the first frequency band (subscriber terminal) From the CATV center equipment direction) and the downlink communication signal are frequency-superposed, and the node device used in the CATV transmission system in which the uplink and downlink communication signals are time-division multiplexed, wherein the downlink CATV signal and the downlink communication signal A node device, comprising: an optical / electrical converting unit for converting the frequency-superimposed signal of the optical signal into an electrical signal, and an electrical / optical converting unit for converting the upstream communication signal into an electrical signal. 20. The method according to claim 19, further comprising: a separation / superimposition unit that frequency-separates the frequency-superimposed optical-electrically converted signal and further superimposes the frequency, and a combining unit that combines upstream and downstream communication signals. The node device described. 21. The node device according to claim 20, wherein said separating and superposing means is composed of a directional filter. 22. The node device according to claim 21, wherein the directional filter is configured to be exchangeable so that a separation frequency band can be set arbitrarily. 23. The node device according to claim 19, further comprising monitoring means for monitoring the downlink CATV signal and the uplink and downlink communication signals. 24. The node device according to claim 20, further comprising a bidirectional amplifier that amplifies the upstream and downstream communication signals that are separated and superimposed by the separating and superimposing means. 25. The node device according to claim 24, wherein said amplifying means comprises a router. 26. The node device according to claim 20, further comprising a unidirectional amplifying unit that amplifies the downlink CATV signal that is separated and superimposed by the separating and superimposing unit. 27. The node device according to claim 20, wherein the coupling means is composed of a changeover switch which is controlled by a time division control signal. 28. A monitoring device for use in the center device according to claim 13, which monitors the downlink CATV signal and the uplink and downlink communication signals. 29. A monitoring device used in the node device according to claim 19, for monitoring the downlink CATV signal and the uplink and downlink communication signals. 30. A bidirectional amplifier used in the node device according to claim 19, which amplifies the upstream and downstream communication signals that are frequency-separated and superimposed. 31. A unidirectional amplification means for amplifying the downlink CATV signal, which is provided between the node device according to any one of claims 19 to 27 and the subscriber terminal, and amplifies the upstream and downstream communication signals. A repeater including a bidirectional amplifying means.